1. Field of the Invention
The present invention relates to a vehicle periphery displaying apparatus for displaying a vehicle periphery situation.
2. Description of Related Art
There is known a technique of displaying a vehicle periphery image synthesized from two images: one is an image captured by a camera to show a situation of a vehicle periphery in real-time; and the other is a synthetic image, which is synthesized from an image of the vehicle and an image that covers an area currently located outside a field of view of the camera due to backward movement of the vehicle. Such technique is described in JP-2003-189291A and JP-2006-327498A for instance.
According to a technique described in JP-2003-189291A, data of an image captured by a camera is converted by being projected onto a ground coordinate system, and thereby a bird's eye view image taken from a predetermined viewpoint (corresponding to location of the camera) is successively produced. Because of the above process, an image to be displayed is different from a raw image with characteristic distortion. A first bird's eye view image produced based on previous shot of the camera is displaced in accordance with movement of the vehicle to produce a post-displacement bird's eye view image. A synthetic bird's eye view image is synthesized from the post-displacement bird's eye view image and a second bird's eye view image produced based on the newly shot of the camera. Further, the synthetic bird's eye view image is converted into a projection image, so that the projection image looks like an image captured by a camera. The projection image is displayed with a monitor.
According to a technique described in JP-2006-327498A, a drawing processer corrects for the distortion, which results from a wide angle lens, of a presently-captured image and a previously-captured image, so that the corrected images have no distortion. From the corrected previously-captured image, the drawing processer extracts only the data representative of an area close to the vehicle, thereby producing data of a past image for image synthesizing. Further, the past image is converted into an image taken from a virtual view point that is located above a center of a rear axel of the vehicle.
From the corrected presently-captured image, the drawing processer extracts only the data representative of an area distant from the vehicle, thereby producing data of a current image for image synthesizing. Further, the drawing processer performs size reduction on the data of the current image at a predetermined reduction rate to produce the reduced data. The drawing processer superimpose the reduced data of the current image on a synthetic area of the data of the past image whose viewpoint has been converted, thereby producing a synthetic image and displaying the synthetic image on a display screen. Further, the drawing processer coverts a vehicle width extension line and a rear tire line in accordance with the virtual viewpoint and displays the converted, vehicle width extension line and the converted rear tire line on the display screen.
The inventors of the present application have found that the above-described conventional techniques involve the following difficulties. Since the above-described conventional techniques perform a variety of image processing (e.g., correction of distortion, viewpoint conversion, size reduction and the like) on an image captured by a camera, a large amount of data is involved in the computation, and a microcomputer is required to have a large computational power. Further, since the conventional technique corrects an image captured by a camera and displays the image without distortion, the displayed image without distortion may be easily viewable on a screen but an area covered by the displayed image becomes disadvantageously small.